Processing and properties of poly(ester–urethane)/modified montmorillonite nanocomposite foams derived from novel diol and tolylene-2,4-diisocyanate

Abstract

In this attempt, we have designed novel poly(ester–urethane) (PEU) using poly(di(ethylene glycol)/trimethylolpropane-alt-adipic acid), tolylene-2,4-diisocyanate, and novel diol. Later, PEU has been employed for the fabrication of nanocomposites and foams with hydroxyl-modified montmorillonite (MMT-OH) via in situ polymerization. Afterward, structure and physical properties of PEU/MMT-OH nanocomposites and foams have been explored using various techniques. Physical characteristics of nanocomposites and foams seemed to be dependent upon polyurethane structure, modification of layered silicate and physical interaction between matrix and organoclay platelets. Field emission scanning electron microscopy revealed distorted honeycomb morphology of PEU/MMT-OH 1–5 foams, while PEU/MMT-OH 1–5 nanocomposites depicted dispersed MMT-OH in the matrix. Increased cell density in nanocomposite foams was also observed relative to pure PEU foam. PEU/MMT-OH 5 (5 wt% MMT-OH) foam showed improved tensile strength of 58.1 MPa relative to PEU/MMT-OH 1 foam (56.8 MPa). The density of the foams was also increased (0.7–1.7 g cm−1) with clay loading. The 10% thermal decomposition temperature of PEU/MMT-OH 1–5 foams measured by thermogravimetric analysis was in the range of 431–465°C. Percentage of water absorption was also measured for the foam materials. Dynamic mechanical thermal analysis of PEU/MMT-OH 5 foam with 5 wt% nanofiller showed higher glass transition temperature ( Tg) of 129°C relative to PEU/MMT-OH 1 ( Tg 116°C). UL 94 and limiting oxygen index results showed that PEU/MMT-OH 1–5 foam had increased nonflammability (V-0 rating) with the clay loading. Silicate layers of MMT-OH were well exfoliated in PEU matrix due to chemical reaction between the hydroxyl of MMT-OH and functional groups of PEU. The morphology, mechanical, thermal, and flame retardant properties of PEU/MMT-OH 1–5 foams were found to be superior to those of PEU/MMT-OH 1–5 nanocomposites.